The technical journal "Automobiltechnische Zeitschrift" (ATZ) 82 (1980) 4 includes an article entitled "Verringerung des Kraftstoffsverbrauchs von Ottomotoren durch elektronische Steuerung von Einspritzung und Zundung". On page 173 of this article, a paragraph 3.5 is directed to the digital engine electronics. In this paragraph, in addition to various lambda values, also the ignition time points can be set to values which are matched with the particular lambda value. FIG. 6 on page 173 shows an ignition characteristic field expanded over intake pipe pressure and rotational speed.
U.S. Pat. No. 4,178,891 relates to a method for controlling the operational performance of an internal combustion engine. A method is disclosed for controlling the smoothness of the operation of an engine and provides that the ignition angle in addition to the change of the fuel/air mixture and/or the quantity of exhaust gas fed back is changed. A combined displacement of the ignition angle, the lambda value or the exhaust gas quantity fed back is proposed in the context of a smoothness control.
European patent 0,033,616 discloses a control system for the idle speed wherein the ignition displacement is displaced in proportion to the deviation between the actual and desired speeds and the air or mixture intervention by means of an integral component based on the actual-desired speed deviation is controlled out.
The cooperative relationship between lambda control and idle speed control has been shown not to be optimal in known systems having lambda control and idle speed control. In principle, the two functions of idle speed control and lambda control operate completely independently of each other. However, since both are coupled via the engine, unpleasant operational conditions can occur because the controllers can also operate against each other in dependence upon operating range. The torque supplied by the engine is a function of lambda. If the lambda value changes, this has an influence on engine speed via the changed torque. Since the speed in idle should be held constant, the engine speed controller must intervene immediately in order to reverse the lambda influence. Accordingly, a poor operation of the engine can result at idle in the presence of unfavorable phase conditions for the two controller interventions.